1. Field of the Invention
The present invention relates to a mixed reality presentation technique.
2. Description of the Related Art
There are conventionally mixed reality (MR) presentation apparatuses. For example, a mixed reality presentation apparatus comprises an image display means (e.g., HMD: Head Mounted Display), a physical image capturing means, a virtual image generation means, a position and orientation detection means (e.g., position and orientation sensor), and a composition means for compositing the physical image and virtual image.
A typical example of the physical image capturing means has a small camera attached to the HMD to capture the scene in front of the HMD and records the captured image in the memory of a computer.
The position and orientation detection means is used to detect, for example, the position and orientation of the physical image capturing means. For example, a magnetic position and orientation sensor is attached to the detection target (e.g., a small video camera serving as the physical image capturing means) to detect its position and orientation. The magnetic position and orientation sensor detects the relative position and orientation between a magnetic field generator (transmitter) and a magnetic sensor (receiver). The position and orientation sensor can detect the three-dimensional position (X,Y,Z) and orientation (Pitch,Yaw,Roll) of the sensor in real time.
The virtual image generation means lays out a three-dimensionally modeled CG in a virtual space with the same scale as the physical space and renders the scene of the virtual space from the same position and orientation as those of the small video camera upon capturing the physical space, thereby obtaining a CG image.
The composition means generates a mixed reality image by superimposing the virtual image obtained by the virtual image generation means on the image obtained by the physical image capturing means. For example, the composition means writes an image captured by the physical image capturing means in the video memory of a computer and then writes a CG image obtained by the virtual image generation means on the captured image.
When the image display means displays the thus obtained mixed reality image on the image display device (e.g., HMD), the observer can feel as if a virtual object (CG) appeared in the physical space.
Another system has an operation input means added to a mixed reality presentation apparatus so that, for example, the position and orientation of a virtual object (CG) can be operated. An example of the operation input means is an operation input device for games (e.g., Japanese Patent Laid-Open No. 2000-353248; corresponding to U.S. Pat. No. 6,972,734).
Some arrangements have no physical image capturing means. In this case, the image display device itself needs to be optically see-through and capable of observing the physical space before eyes. In this case, it is only necessary that the virtual image generation means displays the virtual object, and no composition means is required.
There is also a system which allows not only one person to observe and operate a mixed reality space but a plurality of persons to simultaneously experience and operate a single mixed reality space. In this case, a virtual scene management means for managing the state of the scene of the virtual space is provided. The virtual image generation means of each observer renders the virtual space image from his/her viewpoint of observation based on scene information obtained from the virtual scene management means. This allows every observer to observe the scene with the same contents from his/her viewpoint. When a plurality of operation input devices are prepared, the observers can operate the same virtual space.
According to such a system configuration, every observer can observe the mixed reality space simultaneously from the viewpoint of his/her own and operate a virtual object.
The conventional mixed reality presentation apparatus sometimes determines the operation contents by combining observer information such as the direction of line of sight of each observer with information input to the operation input device. An example will be described. FIG. 11 is a view showing a state wherein each of two observers is observing a mixed reality image.
Observers 1101 and 1102 wear HMDs 1103 and 1104 on heads and hold operation input devices 1105 and 1106 in hands, respectively. FIG. 12 is a view showing an example of the operation input device applicable to the operation input devices 1105 and 1106. Referring to FIG. 12, a cursor button 1206 inputs instructions to move a virtual object as an operation target to the far, near, right, and left sides. For example, the user can input an instruction to move a virtual object as an operation target to the far side by pressing the cursor button 1206 in the direction of X. Buttons 1202 to 1205 are used for inputting various kinds of instructions.
The operation input device connects to a computer (not shown) via a cable 1201. Operation instructions by the cursor button 1206 or buttons 1202 to 1205 are sent to the computer via the cable 1201.
Referring back to FIG. 11, a virtual object 1107 is the operation target of the operation input devices 1105 and 1106. An explanatory arrow 1199 indicates the far side for the observer 1102 along his/her line of sight. An explanatory arrow 1198 indicates the far side for the observer 1101 along his/her line of sight. In this example, the observer 1101 can input an instruction to move the virtual object 1107 in the direction of the arrow 1198 by using the operation input device 1105 (e.g., by pressing the cursor button 1206 in the direction of X). The observer 1102 can input an instruction to move the virtual object 1107 in the direction of the arrow 1199 by using the operation input device 1106 (e.g., by pressing the cursor button 1206 in the direction of X).
In this case, each observer wants to move the virtual object 1107 in the direction to increase the distance from him/her (to the far side viewed from him/her). The moving direction of the virtual object 1107 can change in accordance with the direction of line of sight of each observer even when the same key operation is executed (the cursor button 1206 is pressed in the direction of X), resulting in a convenient operation method.
As another example of the operation method of determining the operation contents by using observer information such as the direction of line of sight of an observer, one of a plurality of virtual objects may be selected by selecting a virtual object closest to the screen center in the image seen by the observer upon pressing a button.
As described above, conventionally, determination is done based on both observer information (the position and orientation of the observer's head or the information of the observed screen) and operation input information from an operation input device and reflected on the operation.
Additionally, if an observer is going to change a set value (e.g., color setting of the display) of his/her HMD by using the operation input device, it is necessary to manage the association between the observer information (which observer is wearing which HMD) and the operation input device to specify the target HMD whose set value is to be changed by the information input to the device.
According to the conventional method, operation input devices and image display devices need to be associated in advance, resulting in cumbersomeness. A problem is posed if the number of operation input devices is smaller than that of image display devices. This problem will be described below in more detail.
In the example shown in FIG. 11, a plurality of persons share a single mixed reality space and execute a cooperative operation, as described above. In FIG. 11, the operation input device 1105 is associated with the HMD 1103 in advance. When the observer 1101 who is wearing the HMD 1103 presses the cursor button 1206 of the operation input device 1105 in the direction of X, the direction of line of sight of the HMD 1103, that is, the direction of line of sight of the observer 1101 (direction of arrow 1198) is interpreted as the “far side”. Hence, the virtual object 1107 moves in the direction of arrow 1198.
Similarly, when the observer 1102 presses the cursor button 1206 of the operation input device 1106 in the direction of X, the direction of line of sight of the observer 1102 (direction of arrow 1199) is interpreted as the “far side”. Hence, the virtual object 1107 moves in the direction of arrow 1199.
If the observer 1101 erroneously takes the operation input device 1106 and presses the cursor button 1206 in the direction of X, the direction of line of sight of the observer 1102 is interpreted as the “far side” so that an operation result unwanted by the observer 1101 is obtained (the virtual object 1107 moves to the “near side” of the observer 1101). To prevent this, each of the observers 1101 and 1102 must take care which operation input device should be held in correspondence with his/her HMD, resulting in cumbersomeness. In addition, it is impossible to allow a plurality of observers to share one operation input device. As many operation input devices as observers must be prepared.